Can moisture be captures there? If I were you I'd go on ebay and look at some pics of similar cars. I'll bet there are quite a few on there that will have close-up pics or close enough pics to tell you how big of a gap. I'll try and measure my dad's gap on his 300E.
David

(edit): The mechanic did replace the gasket didn't he?

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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